This partially reverts fe65e9c8.

In the referenced commit I removed @ret from
virHostValidateBhyve() thinking it wasn't used when in fact it is
- it's usage is hidden under MODULE_STATUS_WARN(). Reintroduce
the variable back.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>